I've been seeing some strange behavior in the z1's I'm using. On the last few projects I required a wide, static camera. I set the cam to manual and perform a white balance, and then just leave it to capture the action. However, every now and then you can see the recording slowly pulsates from the set white to either blue or yellow, i.e an unbalanced setting, and then back to the set white and so on.
I basically end up with video that slowly fades between balanced and unbalanced, very smoothly and regimented - seemingly mechanical rather than reacting to natural environment. This stops if I set it to auto!

I experienced the same effect a long time ago when I used a Z1 for a static shot. However, the problem occurred only when the camera was set to "auto white balance." I realized after the shoot that an oscillating fan had been set up near to, but off to the side of my camera and that the color shift was in sync with the fan's movement. That's why I suspect the shift may have been caused by the changing temperature (but don't ask me how). I noticed this effect one more time on an outdoor shoot (again, very early in my career when I had the white balance set to "auto). In the second case though, the color shift took about two minutes to go from cool to warm and back to cool again.

I have been working with a manual white balance setting ever since and have never had the same problem...at least none that I've been able to notice.